Field of the Invention
The present invention relates to a cooling and isolating structure for the external casing of a hot air blowing gun, comprising an insulating embedded plate with excellent insulating effect to isolate the interior of the hot air blowing gun and the nozzle, to define an insulated and cooling isolated space to effectively isolate the heat conducted from the casing pipe to the hot air blowing gun, and to prevent the external casing of the hot air blowing gun from being deformed by overheating.
The U.S. Pat. No. 6,370,326 discloses a hot air blowing gun comprising an inner barrel with high-impedance heating wire inside and a fan motor assembly at its rear end for blowing the heat outward. A tapered nozzle is installed to the front end of the inner barrel. An outward positioning flange with a plurality of through holes on its surface is disposed on the bottom side of the nozzle such that the outward positioning flange can be fixed onto the inner edge of the front end of the hot air blowing gun, while keeping a predetermined distance between the nozzle and its surfaced. A protective cap with appropriate convergence is disposed correspondingly to the front end of the hot air blowing gun and keeps a gap between the periphery of the nozzle. During the assembly of aforementioned components, the nozzle and inner barrel can be installed and fixed onto the inner edge of the front end of the hot air blowing gun, and the protective cap can be installed on the periphery at the front end of the hot air blowing gun. Thus, when the user turns on the hot air blowing gun, the fan motor assembly blows away the high-temperature heat produced by the heating wire in the inner barrel in a direction, and on the other hand, it will produce wind to pass through the through holes on the flange around the inner barrel, and blow out from the gap between the protective cap and the nozzle. Since the heating wire is disposed inside the inner barrel, and the heat is insulated properly by the wall of the inner barrel so that the temperature on the outside of the inner barrel is relatively low. The cooler airflow blown out from the flange of the nozzle and the through holes can effectively lower the contact temperature of the flange and the inner periphery of the hot air blowing gun. Therefore, such an arrangement can prevent the hot air blowing gun from accumulating heat or being deformed, and thus it accomplishes a safer effect for high temperature control.
However, even though an appropriate gap for isolation is kept between the inner barrel and the external casing of the hot air blowing gun, the cold airflow can pass through and attain the effect of insulating the heat and cooling the external casing of the hot air blowing gun. Due to the flange having a plurality of through holes disposed on the nozzle, which is in contact at an angle of 360 degrees with the external casing of the hot air blowing gun, there is solid substance between the through holes of the flange and the through holes, which blocks the cold airflow and enhances the effect of conducting heat so that the high temperature heat inside the nozzle can be conducted to the surrounding of the flange through the physical section of the flange. Therefore, the heat produced will focus easily on the flange, and further cause an extremely high temperature in the flange, so that the position, where the external casing of the hot air blowing gun and the flange are in contact, has larger impact of high temperature on a larger contact area, which may easily cause partial deformation to the external casing. Particularly, if the hot air blowing gun has been used continuously for a long time, the situation of the deformation will be very serious. Therefore, the prior-art hot air blowing gun is not suitable for being used continuously for a long time.
Further, the hot air blowing gun uses a fan motor assembly to draw in the air from outside of the gun and to blow the hot air produced by the thermal resistor in the inner barrel to supply hot air to users. Therefore, the dust and cotton fiber in the air will flow into the gun together with the airflow. After the hot air blowing gun has been used for a long period of time, the dust and cotton fiber will accumulate in the gun. Similarly, dust and cotton fiber will also accumulate on the circular wall of the nozzle reducing the diameter of the through hole and decreasing the airflow, and thus greatly reducing the cooling effect of the nozzle, which can easily cause partial deformation to the hot air blowing gun, and shortening the life of the hot air blowing gun.
Therefore, in order to improve the insulating effect between the hot air blowing gun and the nozzle according to the prior art, an embedding ring is disposed at the rear end of the nozzle so that the embedding ring can be embedded and secured onto the insulating embedded plate. The insulating embedded plate can be secured on the inner side of the external casing in order to maintain an appropriate distance between the nozzle and the external casing of the hot air blowing gun. Since the insulating embedded plate is made of excellent insulating and heat-resistant materials and has a plurality of ventilation holes, it isolates the heat of the nozzle, and the high heat produced by the nozzle will be carried away by the cold air between the nozzle and the sleeve. Therefore, it will not have any effect of conducting high heat to the external casing, and assures that the external casing will not be deformed or produce heat. Such arrangement makes the application of the hot air blowing gun safer and more reliable.